The present invention relates to biological engineering, and more particularly, to a small scale device for holding live cells which may be fused by applying predetermined electric signals to the device.
The electro cell fusion process is generally done in several phases. In the first phase, the cells are brought close to each other to form pearl chains by exposing the cells to an alternating electric field. In the second phase, the cells which are in contact with each other are exposed for a brief moment to an alternating field of higher amplitude than the initial alternating electric field. The cells are pushed against each other and flatten out in the area of contact. In the third phase, cell fusion is initiated by one or more short, unidirectional pulses of high voltage. Under the correct conditions, pores in the cell membranes will open up and adjacent cells will fuse with each other. If the voltage is too high or the pulses too long, cell damage can occur and a non-viable hybrid results. There are particular parameters for optimal fusion yield for different cell types. In the fourth phase, the alignment alternating electric field is reapplied to maintain mechanical confinement and to aid in rounding off the fused cells.
Two physical processes are involved in the four phases of electro cell fusion. Dielectrophoresis governs the movement of the cells, i.e. alignment, compression and post fusion. Dielectric breakdown governs the actual fusion event.
Glass microscope slides have heretofore been provided with electrodes to enable small scale electro cell fusion. In some cases, the electrodes have taken the form of small wires extending across the top of the glass slide. Such a device is commercially available from GCA Corporation of Chicago, Ill. In another version, flat metal electrodes overlie the glass slide. Such a device is commercially available from D. E. P. Systems, Inc. of Metamora, Miss. In the foregoing devices, a droplet of fluid containing the cells to be fused is deposited on top of the electrodes and is held in place by capillary action. The construction of a small electro cell fusion device with a clear glass slide enables the four phases of the process to be observed through a microscope.
Other small electro cell fusion devices maintain the cell suspension fluid in a closed loop to permit repetitive sterile injection of fresh cells, with fused cells exiting the opposite end. Examples of this type of device are illustrated in FIG. 6 of U.S. Pat. No. 4,441,972. Another such device is called the "closed" design available from D. E. P. Systems, Inc.